Excess carbohydrates

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Is there such as thing as too much carbs? Excess carbohydrates & de novo lipogenesis

This topic always fascinated me!

“What would happen if you significantly overfed on carbohydrates?” i.e. once your carbohydrate stores were full, what would happen to the excess carbohydrates. Fortunately, the guys at Mac-Nutrition unearthed a gem of a paper HERE – arguably one of my favourite papers to date! Do you even have a favourite paper… sort it out. The reason this paper is so cool is that it dispels a number of myths in the nutrition industry, and highlights an important facet of pre performance nutrition.

Title: Glycogen storage capacity and de novo lipogenesis during massive carbohydrate overfeeding in man

First and foremost, what is de novo lipogenesis? De novo lipogenesis is the creation of fat from carbohydrates. Humans have the ability to convert excess carbohydrate into fat, but not fat into carbohydrates. So the questions in my mind were/are:

  • At what point does de novo lipogenesis ‘kick in’ or is it always occurring?
  • How many carbohydrates can you eat until glycogen stores are full/saturated?
  • How many carbs can you consume before de novo lipogenesis increases significantly (to the point at which it’s detrimental to performance)?

Excess carbohydrates and pre performance nutrition

When attempting to increase one’s carbohydrate stores, for example before sports performance, we now know that the traditional glycogen loading protocol of depleting carb stores 4-7 days out from competition through activity and a high fat diet, followed by 3-4 days of a high carbohydrate diet is not required. Instead, a normal, mixed diet 3-7 days out from competition, followed by 1-2 days of a high carbohydrate diet sufficiently elevates glycogen stores to a range that would be conducive to optimum performance.

See my article HERE regarding pre performance nutrition and HERE regarding nutrition for sport performance.

In short, a very high carbohydrate diet, of somewhere between 7 & 10g per Kg of bodyweight in the 24-36 hours before competition should provide the body with performance-enhancing glycogen stores for a sports competition lasting between 60 & 180 minutes. Failure to achieve this level of carbohydrate intake/glycogen storage, and one runs the risk of sub-optimal performance, largely caused by a necessary dip or decline in performance intensity as fatigue sets in earlier than anticipated.

excess carbohydratesSo what did the researchers do? The researchers took three individuals and placed them on a low calorie, high fat, low carbohydrate diet for 3 days. These individuals also completed physical activity over this period. The aim was to diminish the body’s current glycogen stores. 7 days of high calorie, high carbohydrate intake then ensued (something akin to a huge indulgence on pizza and coca-cola, only this was maintained for 7 days and not just a weekend!). After that, the individuals followed a limited yet high protein diet, virtually devoid of carbohydrates, for two days. They then resumed the low calorie, high fat, low carbohydrate diet, that they began the trial consuming.

Study findings

  • A dramatic increase in carbohydrate oxidation – the use of carbohydrates for energy – over seven days of overeating
  • Suppression of lipid oxidation – the use of fat for energy – over seven days of overeating

(The first two findings appear a normal and adaptive response to an excess of carbohydrates. The body simply responds by increasing its reliance on carbohydrates to fuel metabolism, and decrease it’s utilisation of (stored) fat)

  • Roughly 4 days of excess carbohydrate consumption was required to fully saturate glycogen stores

(The authors suggest that total glycogen storage capacity in the body may total somewhere between 800 & 900g. They also hypothesise that this figure may be even higher, in the region of 1 – 1.1kg, for athletes, who may have a genetic/trained ability to store more glycogen. In fact, as a rough guide, they suggest the glycogen storage capacity to be ~15g/kg of bodyweight i.e. for an 80kg individual that would equate to 1200g or 1.2kg)

  • Plasma triglycerides increased tenfold during carbohydrate overfeeding. This is noteworthy, and correlates with diet studies of higher & lower carbohydrate intake which show that low-carb diets tend to reduce circulating blood triglyceride levels. High Triglyceride levels are a risk factor for heart disease
  • Two days of excess carbohydrates appeared to facilitate de novo lipogenesis, which increased further each day of continuous carbohydrate overfeeding
  • The subjects weight at the beginning and end of the trail were not significantly different – in other words, 3 days of restricted calories either side of a 7 day carbohydrate binge, and the subjects did not put on weight (incredible!!)
  • Glucose levels stay remarkably steady, despite an excess of carbohydrates, in otherwise healthy young males

In one paragraphexcess carbohydrates

The findings are just brilliant! Three people massively overfed on carbohydrates for 7 days, bracketed by ~3 days of calorie restricted diets, ended up weighing the same. The body is incredible, maintains very steady blood glucose levels, and can handle large volumes of carbohydrates well (remaining in a very narrow range). And de novo lipogenesis is a perfectly well-suited mechanism for dealing with significant excess carbohydrates.

So now you know: prior to performance, increase the consumption of carbohydrates in the day or two before competition, in order to elevate levels of muscle glycogen. Most people appear to have the capacity of between 600 & 900g stored glycogen. Do not worry about the creation of fat from your carbohydrate intake; huge quantities of carbohydrates are required for multiple, successive days, in order for de novo lipogenesis to increase by any appreciable level. Where excess carbohydrate consumption does occur, the body responds with increased energy expenditure, increased carbohydrate oxidation, and de novo lipogenesis.

Take home:

  • The body can tolerate excess carbohydrates whilst maintaining very steady blood glucose levels
  • The body can store excess carbohydrates as glycogen
  • 3-4 days of excessive carbohydrate intake is required before de novo lipogenesis is upregulated to any substantial degree. Until then, de novo lipogenesis is not the primary fate of excess carbs
  • After severe indulgence in excess calorie and excess carbohydrate consumption, the implementation of a calorie deficit almost completely eradicates any weight gain that may have occurred
  • Carbohydrate intake may increase overall weight, largely due to the stored energy itself and the fluid with which it is accompanied. This is transient, and is easily lost on a low calorie, low carbohydrate diet or where one completes physical activity